Molecular interactions between hosts and pathogens Partho Ghosh Department of Chemistry & Biochemistry and Section of Molecular Biology University of California, San Diego

PathogensHost cells Virulence Factors Host Cell Target Establishment of niche in host Subversion of host defenses and immunity Proliferation in host Transmission to other hosts Infectious Diseases at the Molecular Level

Type III Secretion Needles Kubori et al., Science 280:602 (98) Pathogenic bacterium Human cell

Type III Secretion System (TTSS) Gram-negative Pathogens of mammals –Escherichia coli –Pseudomonas aeruginosa –Salmonella tymphimurium –Shigella flexneri –Bordetella pertussis –Chlamydia trachomatis –Yersinia spp. Pathogens of plants –Erwinia amylovora –Pseudomonas syringae –Ralstonia solanacearum –Xanthomonas campestris

Pseudomonas aeruginosa Ubiquitous and antibiotic-resistant bacterium Problem for patients with weakened immune systems Certain strains cause severe and acute infections 90% of severe and acute strains — inject the protein ExoU into human cells, results in cell death CDC

Phospholipase A 2 motifs — destroy mammalian cell membranes But, overall identity to phospholipase ~10% How does ExoU function? Using genome sequences to get the answer Phillips et al. JBC (03)

Testing the phospholipase idea: Syringe Loading Clarke & McNeil. (1992) J Cell Sci 102: mammalian cells + ExoU ?

ExoU kills mammalian cells and needs sites 1 and 2 Cell Death ExoU Site 1 Site 2

ExoU needs a mammalian cell component ExoU-GFP

Learning what that component is using yeast Yeast making ExoU Yeast without ExoU

ExoU kills cells but Phospholipase inhibitors block cell death Cell Death Inhibitors

Will inhibitors stop Pseudomonas? Pseudomonas aeruginosa + inhibitor

Inhibitors protect against Pseudomonas Cell Death Pseudomonas w/o ExoU Pseudomonas + Inhibitor Pseudomonas

Current Ann Cai Alicia Gamez Jyothi Kumaran Case McNamara Jason Miller Rebecca Phillips Catarina Raposo Loren Rodgers UCSD Ed Dennis David Six Lorraine Pillus William Fenical University of Toronto Charlie Boone Funding W.M. Keck Foundation Cystic Fibrosis Foundation